8G8 
MR. G. J. ROMANES AND PROFESSOR J. C. EWART 
2. PedicellaricB .—No effect whatever is produced upon these organs by destruction 
of the nerve-ring. 
3. Spines .—These organs, on the other hand, are profoundly affected—not, indeed, 
as regards their spontaneity and the function which they share with the pedicellarise 
of closing round any instrument of stimulation, but as regards their other two more 
general functions. That the particular or local function which they share with the 
pedicellarise should not be impaired by destruction of the general nerve-centre is no 
more than we might expect from those experiments detailed in previous parts of this 
paper, which proved that tins function is performed exclusively by the numberless 
local nerve-centres (cells) of the external plexus. Thus, for instance, it will be 
remembered that when a small piece is cut out of the shell of an Echinus or 
Spatqingus, and the internal surface of that piece painted with acid, its spines and 
pedicellariee, although severed from any possible nervous connexion save those of 
the external plexus, will continue to perform their function of localising a seat of 
stimulation. 
As regards, then, the more general function of the spines, we have first to consider 
what we may term their general reflex irritability— i.e ., their power of active bristling 
response all over the animal when any part of its surface is strongly stimulated, as by 
burning. Immediately after the operation of removing the nerve-centre this function 
is found to be in abeyance, or nearly so—strong stimulation of one part of the animal 
not being followed by any response of the spines in other parts. This effect, however, 
completely passes off within several hours after the operation, and is therefore to be 
attributed to shock. The fact, however, that the influence of shock is thus revealed 
in temporarily suspending this general nervous communication among the spines, 
proves that this general communication, unlike the more special one which they share 
with the pedicellarise, is itself in communication with the central nervous ring. Fur¬ 
ther, the experiments detailed in a previous part of this paper prove that the medium 
of communication is in this case the hypothetical internal nervous plexus, as in the 
case just mentioned the medium of communication has been proved to be the external 
nervous plexus. And as the effect of the operation in question is only transitory 
—after recovery from shock the spines being as responsive as ever to severe stimu¬ 
lation—we must conclude that the general communication between the spines is 
maintained by the direct conductility of the supposed internal plexus, and is not of 
the nature of a reflex in which the nerve-ring is concerned as a general centre. The 
only effect of removing this nerve-ring is temporarily to paralyse, through shock, the 
supposed internal plexus with which the ring is connected. 
Lastly, the effect of removing the nerve-ring is that of completely and permanently 
destroying the general co-ordination of the spines ; that is to say, after this operation 
these organs are never again of any use to the Echinus for the purpose of locomotion. 
When the animal is placed upon a table and a lighted spirit lamp held against one 
side, although all the spines will manifest their active bristling movements, they will 
